Short and to the point.
With apologies to the few atheists I know that aren't a**holes.
From the always thought-provoking site of Vox Day:
Agnostic: "I doubt there is a God. Because I haven't seen the evidence."
Atheist: "There is no God. Because I'm an a**hole."
That's funny! And not too far off base.
Interestingly, the conservative and/or libertarian atheists I interact with, basically don't speak of religion, other than to state that it is not their cup of tea. And I think they probably hedge more agnostic, anyway. Perhaps they harbor great amounts of disdain for Christians (although I doubt it), but at least they keep it to themselves.
Liberal atheists, on the other hand, seem to oft times be insufferable jerks about their advanced, superior, pragmatic beliefs and my stupid, child-like, un-evolved ignorant beliefs.
But try to criticize their religions of global warming and abortion, and all of a sudden you're intolerant and more ignorant than before. They can be downright nasty, shrill, and even nonsensical in their self-righteous screeds.
Think Amanda Marcotte and Machinist Scott.
They almost seem scared of, or threatened by, people's faith.
The actual beliefs that the whole creation of the universe, and mankind itself, are accidental occurrences are monumental exercises in faith, if you ask me.